Chronic rejection, clinically diagnosed as Bronchiolitis obliterans Syndrome (BOS), is the most significant long term cause of morbidity and mortality following human lung transplantation (LTx). Recent studies, including from our laboratory, have demonstrated that BOS is an immunologically mediated process resulting in injury to the pulmonary epithelial and/or the endothelial cells. Recently, we have obtained evidence for an obligatory role for immune responses to lung associated self-antigens (Ags) and cross talk between immune responses to self-Ags and allo-Ags in pre-disposing for the development of BOS following LTx. Additionally, primary graft dysfunction (PGD), which occurs at an alarming rate of 70-80% post-LTx, is an independent as well as a major risk factor for the development of BOS. Analysis of a cohort of recent LTx recipients (142 from our center) has demonstrated that 30% have pre-existing Abs to self-Ags (collagen V (ColV) and K-alpha 1 Tubulin (K?1T)) and these patients demonstrate an increased risk of developing PGD (odds ratio of 3.09, (p<0.02), increased levels of pro-inflammatory cytokines (p<0.01) and increased risk of developing Abs to mismatched donor HLA (p<0.001). More significant is that the patients with pre-existing Abs to self-Ags also are at increased risk (2.3 fold higher) for developing BOS. Since development of PGD following human LTx is very high (>75%) and PGD is a major risk factor for the development of BOS the first goal of this application is to test the hypothesis that down regulation of pre-existing autoimmunity to self-Ags prior to LTx will abrogate interactions between pre-existing Abs to self-Ags and their determinants on lung parenchyma which are exposed during transplantation induced stress. This will result in a marked reduction in the incidence and severity of PGD which will lead to reduction in the proinflammatory cytokine surge, down regulation of both autoimmune and alloimmune responses resulting in prevention of development of both acute as well as chronic rejection. During this proposal, we will identify candidates waiting for LTx at our center as well as at the Cleveland Clinic with pre-existing Abs to self-Ags (ColV and K?1T). These patients with Abs to self-Ags will be enrolled in a pilot clinical trial to be treated with IVIG and Rituximab. We will determine the effect of this treatmen regimen in; 1) reducing the levels of Abs to self-Ags using ELISA, 2) reducing PGD development post-LTx (determined by ISHLT criterion), 3) reducing the levels of pro-inflammatory cytokines (IFN-?, IL-6 and IL-17) in the serum (determined by Luminex), 4) decreasing the frequency of cells secreting pro-inflammatory cytokines (IFN-? and IL-17) upon stimulation with donor Ags and self-Ags (ColV and K?1T) (using ELISPOT), 5) decreasing de novo development of Abs to mismatched donor HLA (measured by solid phase immunoassay), and 6) decreasing the incidence and severity of BOS (determined by ISHLT criterion). We will also identify lung diseases which will pre-dispose for the development of Abs to self-Ags. Control arm for this pilot clinical trial will be patients who currently participate in an ongoing clinical trial of Ab directed therapy for LTx who develop donor specific Abs (DSA) de novo following LTx but do not undergo any desensitization prior to transplant. The second goal is to utilize unique LTx population in our center who are undergoing a multicenter clinical trial based on development of Abs to HLA during the immediate post-transplant period (within 1 year) but having normal pulmonary function following LTx to define the essential role of immune responses to self-Ags and as well as the role of B cells in the development of immune responses to self-Ags and chronic rejection. Towards this, we will analyze all of the LTx patients enrolled in the multicenter clinical trial both pre- and post-transplant as well as post-desensitization for DSA for it's influence on the immune responses to self-Ags. We will also determine the frequency of lung infiltrating B cells with an autoimmune phenotype both in bronchioalveolar lavage and blood. In addition, we will determine their ability to present self-Ag using self-Ag KAT-pentamers. The impact of treatment with Rituximab and IVIG on lung infiltrating B cells, Abs to self-Ags, Abs to donor mismatched HLA and development of BOS will also be determined. Since our preliminary results have shown that a group of LTx patients develop BOS despite absence of DSA or Abs to self-Ags, we propose that cellular immune responses without detectable Abs to self-Ags or immune responses to other yet unidentified lung specific self-Ags may play a role in the induction of BOS. Therefore, the third goal is to identify the cohort of patients without DSA and Abs to self-Ags both pre- and post-LTx who developed BOS and to determine; a) cellular immune responses and cytokines (IFN, IL17 and IL10) produced following stimulation with either allo or self-Ag (K?1T, ColV), and b) whether the sera will have Abs specific for other auto-Ags present in the lungs using a protoarray. The overall goal of this proposal is to employ a safe and effective treatment regimen that targets B lymphocytes prior to and following LTx with the goal of reducing or removing Abs to self-Ags and HLA. The results from this study will determine the essential role of B cells and self-Ags in: 1) incidence and severity of PGD; 2) pro-inflammatory events immediately following LTx; 3) immune responses to both allo and self-Ags; and 4) prevention of development of chronic rejection following human LTx which will result in long term allograft and patient survival.